This invention relates to a method for the mobilization of metal ions in soils and on other surfaces and more particularly to a method using reducing agents in conjunction with indigenous microorganisms to mobilize hazardous metals bound to soils and other contaminated solid surfaces.
Among the various environmental concerns, soil and sediment remediation has received considerable attention in recent years because soils and sediments are the ultimate repositories for many metals that cycle in the environment as a result of activities such as mining, electroplating and various manufacturing and industrial processes. In most instances the metals are immobilized in place by being sorbed (physiochemically bound) to surfaces such as soil particles or contaminated equipment.
There is considerable interest in the remediation of contaminated soils and sediments by so-called soil-cleaning techniques and in the prevention of future contamination via removal of hazardous metals from processing streams prior to deposition into receiving waters. Present methods of recovery of waste waters include the use of ion-exchange resins, biosorption, chemical precipitation, electrolysis, reverse osmosis and membrane filtration. A variety of chemical technologies may be of value in the extraction of heavy metals from soils and sediments including washing with: water, salts, complexing agents such as ethylenediaminetetracetate (EDTA) or nitriolotriacetic acid (NTA), mineral acids, strong bases and some organic acids such as citric acid, that are also complexing agents. There is a need to remediate metal contaminants including, but not limited to, such metals as bismuth, cadmium, lead, thorium, uranium and other transuranic metals, by effecting their release from the bound state (i.e., mobilization) so that they can subsequently be removed and recovered. Bioremediation utilizing reducing agents and microorganisms has value for the mobilizations of contaminants because of its potential economic advantage.
It is an object of this invention to provide a process utilizing indigenous microorganisms and reducing agents to effect the mobilization of metal contaminants.
It is another object of this invention to provide a process using the amino acid cysteine, a reducing agent as well as a metal complexing agent, to enhance the microbial effectiveness for the removal of hazardous metals from soil.
Additional objects, advantages and novel features of the invention will become apparent to those skilled in the art upon examination of the following and by practice of the invention.